The rapid development of electronic technology results in wide applications of such electronic technology in most of industrial equipment. To ensure the optimum heat dissipating effects, installation of plural heat dissipating fans in a mechanism may help to exhaust heat by enhancing circulation between air within an enclosed environment of electronic equipment and air from the external environment, to prevent overheating of the equipment, which would cause unstable operation and component damages, and eventually fire hazards, such as in a “computer PC” as a common example.
The rotational speed RPM of conventional heat dissipating fans are adjusted or configured by the manufacture during fabrication, but not by users. Though such a state of operation by fixed rotational speed is able to provide steady airflow, it cannot efficiently discharge heat generated during high load capacity. To maximize the heat dissipating efficiency, some manufactures design the fans to be operated under high rotational speed in order to provide a higher airflow rate, while increasing the operation noises at the same time. It is, thus, relatively difficult to find equilibrium between heat dissipating efficiency and noise interferences in the application of fans of high rotational speed.
As commonly known, the square frame employed by a heat dissipating fan is usually provided with two to four penetrating screw holes at four corners of the frame, where screws are then implemented to secure the heat dissipating fan to a designated location. Such an installation measure has become the standard specifications in the industry.
Accordingly, this invention utilizes the screw holes that are provided to the heat dissipating fan, without altering or destructing the dimensions, installation measure and the basic structure of the original heat dissipating fan, to provide a rotational speed adjusting knob or switch at an appropriate location of one of the screw holes located at the front or back of the heat dissipating fan frame, which frame may either be extruded from aluminum or injection molded by plastic, wherein the knob is individually exposed out of the fan frame to serve as means for the user to manually adjust the rotational speed of the heat dissipating fan at one's desire.